Buckle plate ink jet printing mechanism

ABSTRACT

An ink jet printing device having at least one nozzle connected to an ink supply and having a buckle plate able to be deformed so as to eject ink on demand from the nozzle is disclosed. The buckle plate is constructed from a first material such as polytetrafluoroethylene having a high coefficient of thermal expansion. The plate is heated by an integral heater means constructed from a second electrically resistive material such as copper. The heater is constructed in a serpentine manner so as to allow the expansion of the length of the heater means substantially in accordance with the expansion of the first material. The energy of activation of the buckle plate for the ejection of a drop of ink is less than about 20 microjoules.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

CROSS- REFERENCED US PATENT APPLICATION AUSTRALIAN (CLAIMING RIGHT OFPRIORITY PROVISIONAL FROM AUSTRALAIN DOCKET PATENT NO. PROVISIONALAPPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO798809/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO801409/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO799909/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO803009/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO801509/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO798909/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO801809/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO802409/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO850109/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO802209/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO802309/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO797709/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO849909/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO798609/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO802709/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO939609/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO939909/112,791 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO940209/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP095909/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP237109/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05PO8065 09/113,111 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26PO8051 09/113,074 IJM27 PO8045 09/113,089 IJM28 PO7952 09/113,088 IJM29PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 09/113,100 MEMS02PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 09/113,064MEMS05 PO8011 09/113,082 MEMS06 PO7947 09/113,081 MEMS07 PO794409/113,080 MEMS09 PO7946 09/113,079 MEMS10 PO9393 09/113,065 MEMS11PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses a buckle plate ink jet printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques on ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different types. Theutilization of a continuous stream ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. 3,596,275 by Sweet also discloses a process of a continuousink jet printing including the step wherein the ink jet stream ismodulated by a high frequency electro-static field so as to cause dropseparation. This technique is still utilized by several manufacturersincluding Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweetet al)

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragmmode of operation, by Zolten in U.S. Pat. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectricoperation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4,584,590 which discloses a shear mode type of piezoelectric transducerelement.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. 4,490,728. Both the aforementioned references disclosed ink jetprinting techniques rely upon the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Printing devices utilizing the electro-thermal actuator are manufacturedby manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

Recently, in the proceedings of the IEEE Ninth Annual InternationalWorkshop on Micro-Electro Mechanical System, held in San Diego, Calif.on Feb. 11-15, 1996, there was presented a paper (pages 418-423 of theproceedings) entitled “An Ink Jet Head Using a DiaphragmMicro-actuator”, by Susumu Hirata et al. in which a form of ink jet headutilising a buckling diaphragm was described. The described ink jet headrelied upon a diaphragm being heated so as to cause the diaphragm tobuckle rapidly resulting in the ejection of ink from around thediaphragm, through a nozzle hole.

The aforementioned arrangement due to Hirata et. al. has a number ofsignificant disadvantages. Firstly, the size of the necessary buckleplate as described is approximately 300 microns in diameter which is ofan excessively large size, especially where, as is common, large arraysof ink jet nozzles are required. This is especially the case with apagewidth printhead where many thousands of nozzles may need to beconstructed for each colour outputted.

Further, the Hirata et al. arrangement utilizes an excessive amount ofapplied energy to the actuator. This is evident by the authors'discussion on page 423 where they note that, as the frequency ofoperations increases, the temperature of the diaphragm rises to thepoint where the device is no longer properly operational.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an alternativearrangement of a buckle/diaphragm actuated ink jet print head, simpleand compact in construction however, allowing for a higher speedoperation of the ink jet head through the utilization of substantiallyless energy per ink drop ejected.

In accordance with a first aspect of the present invention there isprovided an ink jet printing device of the type having at least onenozzle connected to an ink supply and having a buckle plate able to bedeformed so as to eject ink on demand from the nozzle. The buckle platecan be constructed from a first material having a high coefficient ofthermal expansion and from a second electrically resistive material forheating the buckle plate. Further the second material can have a lowercoefficient of thermal expansion than the first material and isconstructed in a serpentine manner so as to allow the expansion of thelength of the heater means substantially in accordance with theexpansion of the first material. Preferably the first material comprisessubstantially polytetrafluoroethylene and the second material comprisessubstantially copper. Further, the energy of activation of the buckleplate for the ejection of a drop of ink is less than about 20microjoules and more preferably less than one microjoule.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings which:

FIG. 1 is a perspective view partly in sections of a single ink jetnozzle constructed in accordance with the preferred embodiment;

FIG. 2 is an exploded perspective view partly in section illustratingthe construction of a single ink nozzle in accordance with the preferredembodiment of the present invention;

FIG. 3 provides a legend of the materials indicated in FIG. 4 to 16; and

FIG. 4 to FIG. 16 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, a “roof shooting” ink jet printhead isconstructed utilizing a buckle plate actuator for the ejection of ink.In the preferred embodiment, the buckle plate actuator is constructedfrom polytetrafluoroethylene (PTFE) which provides superior thermalexpansion characteristics. The PTFE is heated by an integral, serpentineshaped heater, which preferably is constructed from a resistivematerial, such as copper.

Turning now to FIG. 1 there is shown a sectional perspective view of anink jet printhead 1 of the preferred embodiment. The ink jet printheadincludes a nozzle chamber 2 in which ink is stored to be ejected. Thechamber 2 can be independently connected to an ink supply (not shown)for the supply and refilling of the chamber. At the base of the chamber2 is a buckle plate 3 which comprises a heater element 4 which can be ofan electrically resistive material such as copper. The heater element 4is encased in a polytetrafluoroethylene layer 5. The utilization of thePTFE layer 5 allows for high rates of thermal expansion and thereforemore effective operation of the buckle plate 3. PTFE has a highcoefficient of thermal expansion (770×10⁻⁶) with the copper having amuch lower degree of thermal expansion. The copper heater element 4 istherefore fabricated in a serpentine pattern so as to allow theexpansion of the PTFE layer to proceed unhindered. The serpentinefabrication of the heater element 4 means that the two coefficients ofthermal expansion of the PTFE and the heater material need not beclosely matched. The PTFE is primarily chosen for its high thermalexpansion properties.

Current can be supplied to the buckle plate 3 by means of connectors 7,8 which inter-connect the buckle plate 3 with a lower drive circuitryand logic layer 26. Hence, to operate the ink jet head 1, the heatercoil 4 is energized thereby heating the PTFE 5. The PTFE 5 expands andbuckles between end portions 12, 13. The buckle causes initial ejectionof ink out of a nozzle 15 located at the top of the nozzle chamber 2.There is an air bubble between the buckle plate 3 and the adjacent wallof the chamber which forms due to the hydrophobic nature of the PTFE onthe back surface of the buckle plate 3. An air vent 17 connects the airbubble to the ambient air through a channel 18 formed between a nitridelayer 19 and an additional PTFE layer 20, separated by posts, e.g. 21,and through holes, e.g. 22, in the PTFE layer 20. The air vent 17 allowsthe buckle plate 3 to move without being held back by a reduction in airpressure as the buckle plate 3 expands. Subsequently, power is turnedoff to the buckle plate 3 resulting in a collapse of the buckle plateand the sucking back of some of the ejected ink. The forward motion ofthe ejected ink and the sucking back is resolved by an ink drop breakingoff from the main volume of ink and continuing onto a page. Ink refillis then achieved by surface tension effects across the nozzle part 15and a resultant inflow of ink into the nozzle chamber 2 through thegrilled supply channel 16.

Subsequently the nozzle chamber 2 is ready for refiring.

It has been found in simulations of the preferred embodiment that theutilization of the PTFE layer and serpentine heater arrangement allowsfor a substantial reduction in energy requirements of operation inaddition to a more compact design.

Turning now to FIG. 2, there is provided an exploded perspective viewpartly in section illustrating the construction of a single ink jetnozzle in accordance with the preferred embodiment. The nozzlearrangement 1 is fabricated on top of a silicon wafer 25. The nozzlearrangement 1 can be constructed on the silicon wafer 25 utilizingstandard semi-conductor processing techniques in addition to thosetechniques commonly used for the construction ofmicro-electro-mechanical systems (MEMS). For a general introduction to amicro-electro mechanical system (MEMS) reference is made to standardproceedings in this field including the proceedings of the SPIE(International Society for Optical Engineering), volumes 2642 and 2882which contain the proceedings for recent advances and conferences inthis field.

On top of the silicon layer 25 is deposited a two level CMOS circuitrylayer 26 which substantially comprises glass, in addition to the usualmetal layers. Next a nitride layer 19 is deposited to protect andpassivate the underlying layer 26. The nitride layer 19 also includesvias for the interconnection of the heater element 4 to the CMOS layer26. Next, a PTFE layer 20 is constructed having the aforementionedholes, e.g. 22, and posts, e.g. 21. The structure of the PTFE layer 20can be formed by first laying down a sacrificial glass layer (not shown)onto which the PTFE layer 20 is deposited. The PTFE layer 20 includesvarious features, for example, a lower ridge portion 27 in addition to ahole 28 which acts as a via for the subsequent material layers. Thebuckle plate 3 (FIG. 1) comprises a conductive layer 31 and a PTFE layer32. A first, thicker PTFE layer is deposited onto a sacrificial layer(not shown). Next, a conductive layer 31 is deposited including contacts29, 30. The conductive layer 31 is then etched to form a serpentinepattern. Next, a thinner, second PTFE layer is deposited to complete thebuckle plate 3 (FIG. 1) structure.

Finally, a nitride layer can be deposited to form the nozzle chamberproper. The nitride layer can be formed by first laying down asacrificial glass layer and etching this to form walls, e.g. 33, andgrilled portions, e.g. 34. Preferably, the mask utilized results in afirst anchor portion 35 which mates with the hole 28 in layer 20.Additionally, the bottom surface of the grill, for example 34 meets witha corresponding step 36 in the PTFE layer 32. Next, a top nitride layer37 can be formed having a number of holes, e.g. 38, and nozzle port 15around which a rim 39 can be etched through etching of the nitride layer37. Subsequently the various sacrificial layers can be etched away so asto release the structure of the thermal actuator and the air ventchannel 18 (FIG. 1).

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer 25, complete drive transistors,data distribution, and timing circuits 26 using a 0.5 micron, one poly,2 metal CMOS process. Relevant features of the wafer 25 at this step areshown in FIG. 4. For clarity, these diagrams may not be to scale, andmay not represent a cross section though any single plane of the nozzle.FIG. 3 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

2. Deposit 1 micron of low stress nitride 19. This acts as a barrier toprevent ink diffusion through the silicon dioxide of the chip surface.

3. Deposit 2 microns of sacrificial material 50 (e.g. polyimide).

4. Etch the sacrificial layer 50 using Mask 1. This mask defines thePTFE venting layer support pillars 21 and anchor point. This step isshown in FIG. 5.

5. Deposit 2 microns of PTFE 20.

6. Etch the PTFE 20 using Mask 2. This mask defines the edges of thePTFE venting layer 20, and the holes 22 in this layer 20. This step isshown in FIG. 6.

7. Deposit 3 microns of sacrificial material 51.

8. Etch the sacrificial layer 51 using Mask 3. This mask defines theanchor points 12, 13 at both ends of the buckle actuator. This step isshown in FIG. 7.

9. Deposit 1.5 microns of PTFE 31.

10. Deposit and pattern resist using Mask 4. This mask defines theheater 11.

11. Deposit 0.5 microns of gold (or other heater material with a lowYoung's modulus) and strip the resist. Steps 10 and 11 form a lift-offprocess. This step is shown in FIG. 8.

12. Deposit 0.5 microns of PTFE 32.

13. Etch the PTFE 32 down to the sacrificial layer 51 using Mask 5. Thismask defines the actuator paddle 3 and the bond pads. This step is shownin FIG. 9.

14. Wafer probe. All electrical connections are complete at this point,and the chips are not yet separated.

15. Plasma process the PTTE to make the top and side surfaces of thebuckle actuator hydrophilic. This allows the nozzle chamber 2 to fill bycapillarity.

16. Deposit 10 microns of sacrificial material 52.

17. Etch the sacrificial material 52 down to nitride 19 using Mask 6.This mask defines the nozzle chamber 2. This step is shown in FIG. 10.

18. Deposit 3 microns of PECVD glass 37. This step is shown in FIG. 11.

19. Etch to a depth of 1 micron using Mask 7. This mask defines thenozzle rim 39. This step is shown in FIG. 12.

20. Etch down to the sacrificial layer 52 using Mask 8. This maskdefines the nozzle 15 and the sacrificial etch access holes 38. Thisstep is shown in FIG. 13.

21. Back-etch completely through the silicon wafer 25 (with, forexample, an ASE Advanced Silicon Etcher from Surface Technology Systems)using Mask 9. This mask defines the ink inlets which are etched throughthe wafer 25. The wafer 25 is also diced by this etch. This step isshown in FIG. 14.

22. Back-etch the CMOS oxide layers 26 and subsequently depositednitride layers 19 and sacrificial layer 50, 51 through to PTFE 20, 32using the back-etched silicon as a mask.

23. Etch the sacrificial material 52. The nozzle chambers are cleared,the actuators freed, and the chips are separated by this etch. This stepis shown in FIG. 15.

24. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets at the back of the wafer.

25. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

26. Hydrophobize the front surface of the printheads.

27. Fill the completed printheads with ink 54 and test them. A fillednozzle is shown in FIG. 16.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the preferred embodiment without departing from the spirit orscope of the invention as broadly described. The preferred embodimentis, therefore, to be considered in all respects to be illustrative andnot restrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers within-built pagewidth printers, portable color and monochrome printers,color and monochrome copiers, color and monochrome facsimile machines,combined printer, facsimile and copying machines, label printers, largeformat plotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications,, the printhead is 100mm long, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 above which matches the docket numbers in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The 1101 to 1145 series are also listed in the examples column. In somecases, print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal Large forceHigh power Canon Bubblejet bubble heater heats the ink to generated Inkcarrier 1979 Endo et al GB above boiling point, Simple limited to waterpatent 2,007,162 transferring significant construction Low efficiencyXerox heater-in- heat to the aqueous No moving parts High pit 1990Hawkins et al ink. A bubble Fast operation temperatures U.S. Pat. No.4,899,181 nucleates and quickly Small chip area required Hewlett-Packardforms, expelling the required for actuator High mechanical TIJ 1982Vaught et al ink. stress U.S. Pat. No. 4,490,728 The efficiency of theUnusual process is low, with materials required typically less thanLarge drive 0.05% of the electrical transistors energy being Cavitationcauses transformed into actuator failure kinetic energy of the Kogationreduces drop. bubble formation Large print heads are difficult tofabricate Piezo- A piezoelectric crystal Low power Very large area Kyseret al electric such as lead consumption required for actuator U.S. Pat.No. 3,946,398 lanthanum zirconate Many ink types Difficult to Zoltan(PZT) is electrically can be used integrate with U.S. Pat. No. 3,683,212activated, and either Fast operation electronics 1973 Stemme expands,shears, or High efficiency High voltage U.S. Pat. No. 3,747,120 bends toapply drive transistors Epson Stylus pressure to the ink, requiredTektronix ejecting drops. Full pagewidth IJ04 print heads impracticaldue to actuator size Requires electrical poling in high field strengthsduring manufacture Electro- An electric field is Low power Low maximumSeiko Epson, strictive used to activate consumption strain (approx. Usuiet all JP electrostriction in Many ink types 0.01%) 253401/96 relaxormaterials such can be used Large area IJ04 as lead lanthanum Low thermalrequired for actuator zirconate titanate expansion due to low strain(PLZT) or lead Electric field Response speed magnesium niobate strengthrequired is marginal (˜10 μs) (PMN). (approx. 3.5 V/μm) High voltage canbe generated drive transistors without difficulty required Does notrequire Full pagewidth electrical poling printheads impractical due toactuator size Ferro- An electric field is Low power Difficult to IJ04electric used to induce a phase consumption integrate with transitionbetween the Many ink types electronics antiferroelectric (AFE) can beused Unusual and ferroelectric (FE) Fast operation materials such asphase. Perovskite (<1 μs) PLZSnT are materials such as tin Relativelyhigh required modified lead longitudinal strain Actuators requirelanthanum zirconate High efficiency a large area titanate (PLZSnT)Electric field exhibit large strains of strength of around up to 1%associated 3 V/μm can be with the AFE to FE readily provided phasetransition. Electro- Conductive plates are Low power Difficult to IJ02,IJ04 static plates separated by a consumption operate electrostaticcompressible or fluid Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a Fast operationenvironment voltage, the plates The electrostatic attract each other andactuator will displace ink, causing normally need to be drop ejection.The separated from the conductive plates may ink be in a comb or Verylarge area honeycomb structure, required to achieve or stacked toincrease high forces the surface area and High voltage therefore theforce. drive transistors may be required Full pagewidth print heads arenot competitive due to actuator size Electro- A strong electric fieldLow current High voltage 1989 Saito et al, static pull is applied to theink, consumption required U.S. Pat. No. 4,799,068 on ink whereupon Lowtemperature May be damaged 1989 Miura et al, electrostatic attraction bysparks due to air U.S. Pat. No. 4,810,954 accelerates the ink breakdownTone-jet towards the print Required field medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop ejection. Fastoperation such as Neodymium Rare earth magnets High efficiency IronBoron (NdFeB) with a field strength Easy extension required. around 1Tesla can be from single nozzles High local used. Examples are: topagewidth print currents required Samarium Cobalt heads Copper (SaCo)and magnetic metalization should materials in the be used for longneodymium iron boron electromigration family (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K.) Soft A solenoid induced a Low power Complex IJ01, IJ05,IJ08, magnetic magnetic field in a soft consumption fabrication IJ10,IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such Fast operation CMOS fab such as as electroplatediron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easyextension CoFe are required [1], CoFe, or NiFe from single nozzles Highlocal alloys. Typically, the to pagewidth print currents required softmagnetic material heads Copper is in two parts, which metalizationshould are normally held be used for long apart by a spring.electromigration When the solenoid is lifetime and low actuated, the twoparts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magneto- The actuator uses the Many inktypes Force acts as a Fischenbeck, striction giant magnetostrictive canbe used twisting motion U.S. Pat. No. 4,032,929 effect of materials Fastoperation Unusual IJ25 such as Terfenol-D (an Easy extension materialssuch as alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8electromigration MPa. lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focussed upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03, IJ09, IJ17, elastic bend reliesupon differential consumption operation requires a IJ18, IJ19, IJ20,actuator thermal expansion Many ink types thermal insulator on IJ21,IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27,IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for each Pigmented inks IJ38, IJ39, IJ40, actuatormay be infeasible, IJ41 Fast operation as pigment particles Highefficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09, IJ17, IJ18, thermo- high coefficient ofbe generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermalexpansion Three methods of Requires a PTFE IJ23, IJ24, IJ27, actuator(CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conductive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multi- Actuator (LSA).available phase drive circuitry Low voltage High current operationoperation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the simplest Simple operation Drop repetition Thermalink jet directly mode of operation: the No external rate is usuallyPiezoelectric ink pushes ink actuator directly fields required limitedto around 10 jet supplies sufficient Satellite drops kHz. However, thisIJ01, IJ02, IJ03, kinetic energy to expel can be avoided if is notfundamental IJ04, IJ05, IJ06, the drop. The drop drop velocity is lessto the method, but is IJ07, IJ09, IJ11, must have a sufficient than 4m/s related to the refill IJ12, IJ14, IJ16, velocity to overcome Can beefficient, method normally IJ20, IJ22, IJ23, the surface tension.depending upon the used IJ24, IJ25, IJ26, actuator used All of the dropIJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided bythe IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, Satellite drops IJ39,IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greaterthan 4.5 m/s Proximity The drops to be Very simple print Requires closeSilverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced The drop the print media orapplications surface tension selection means transfer roller reductionof does not need to May require two pressurized ink). provide the energyprint heads printing Selected drops are required to separate alternaterows of the separated from the ink the drop from the image in the nozzleby nozzle Monolithic color contact with the print print heads are mediumor a transfer difficult roller. Electro- The drops to be Very simpleprint Requires very Silverbrook, EP static pull printed are selected byhead fabrication can high electrostatic 0771 658 A2 and on ink somemanner (e.g. be used field related patent thermally induced The dropElectrostatic field applications surface tension selection means forsmall nozzle Tone-Jet reduction of does not need to sizes is above airpressurized ink). provide the energy breakdown Selected drops arerequired to separate Electrostatic field separated from the ink the dropfrom the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink). provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 Moving parts are IJ13,IJ17, IJ21 shutter to block ink kHz) operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJ15, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered of thegrill holes. High speed (>50 Stiction is kHz) operation can possible beachieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimulation) actuator selects which operating speed phase and amplitudeIJ08, IJ13, IJ15, drops are to be fired The actuators must be carefullyIJ17, IJ18, IJ19, by selectively may operate with controlled IJ21blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 A2 and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet Any of the IJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium. drops is near or applications above air Tone-Jet breakdownDirect A magnetic field is Low power Requires Silverbrook, EP magneticused to accelerate Simple print head magnetic ink 0771 658 A2 and fieldselected drops of construction Requires strong related patent magneticink towards magnetic field applications the print medium. Cross Theprint head is Does not require Requires external IJ06, IJ16 magneticplaced in a constant magnetic materials magnet field magnetic field. Theto be integrated in Current densities Lorenz force in a the print headmay be high, current carrying wire manufacturing resulting in is used tomove the process electromigration actuator. problems Pulsed A pulsedmagnetic Very low power Complex print IJ10 magnetic field is used tooperation is possible head construction field cyclically attract a Smallprint head Magnetic paddle, which pushes size materials required in onthe ink. A small print head actuator moves a catch, which selectivelyprevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric ink jetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, into a high travel, Generally high pp 418-423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High energy is Hewlett-Packard expansion actuatorchanges, construction in the typically required to Thermal Ink jetpushing the ink in all case of thermal ink achieve volume CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal toa direction normal to coupling to ink complexity may be 1J07, IJ11, IJ14chip surface the print head surface. drops ejected required to achieveThe nozzle is typically normal to the perpendicular in the line ofsurface motion movement. Parallel to The actuator moves Suitable forFabrication IJ12, IJ13, IJ15, chip surface parallel to the print planarfabrication complexity IJ33, IJ34, IJ35, head surface. Drop FrictionIJ36 ejection may still be Stiction normal to the surface. Membrane Anactuator with a The effective Fabrication 1982 Howkins push high forcebut small area of the actuator complexity U.S. Pat. No. area is used topush a becomes the Actuator size 4,459,601 stiff membrane that ismembrane area Difficulty of in contact with the ink. integration in aVLSI process Rotary The actuator causes Rotary levers Device IJ05, IJ08,IJ13, the rotation of some may be used to complexity IJ28 element, sucha grill or increase travel May have impeller Small chip area friction ata pivot requirements point Bend The actuator bends A very small Requiresthe 1970 Kyser et al when energized. This change in actuator to be madeU.S. Pat. No. may be due to dimensions can be from at least two3,946,398 differential thermal converted to a large distinct Iayers, orto 1973 Stemme expansion, motion. have a thermal U.S. Pat. No.piezoelectric difference across the 3,747,120 expansion, actuator IJ03,IJ09, IJ10, magnetostriction, or IJ19, IJ23, IJ24, other form ofrelative IJ25, IJ29, IJ30, dimensional change. IJ31, IJ33, IJ34, IJ35Swivel The actuator swivels Allows operation Inefficient IJ06 around acentral pivot. where the net linear coupling to the ink This motion issuitable force on the paddle motion where there are is zero oppositeforces Small chip area applied to opposite requirements sides of thepaddle, e.g. Lorenz force. Straighten The actuator is Can be used withRequires careful IJ26, IJ32 normally bent, and shape memory balance ofstresses straightens when alloys where the to ensure that the energized.austenic phase is quiescent bend is planar accurate Double The actuatorbends in One actuator can Difficult to make IJ36, IJ37, IJ38 bend onedirection when be used to power the drops ejected by one element is twonozzles. both bend directions energized, and bends Reduced chipidentical. the other way when size. A small another element is Notsensitive to efficiency loss energized. ambient temperature compared toequivalent single bend actuators. Shear Energizing the Can increase theNot readily 1985 Fishbeck actuator causes a shear effective travel ofapplicable to other U.S. Pat. No. motion in the actuator piezoelectricactuator 4,584,590 material. actuators mechanisms Radial The actuatorsqueezes Relatively easy High force 1970 Zoltan constriction an inkreservoir, to fabricate single required U.S. Pat. No. forcing ink from anozzles from glass Inefficient 3,683,212 constricted nozzle. tubing asDifficult to macroscopic integrate with VLSI structures processesCoil/uncoil A coiled actuator Easy to fabricate Difficult to IJ17, IJ21,IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35tightly. The motion of process planar devices the free end of the Smallarea Poor out-of-plane actuator ejects the ink. required, thereforestiffness low cost Bow The actuator bows (or Can increase the Maximumtravel IJ16, IJ18, IJ27 buckles) in the middle speed of travel isconstrained when energized. Mechanically High force rigid requiredPush-Pull Two actuators control The structure is Not readily IJ18 ashutter. One actuator pinned at both ends, suitable for ink jets pullsthe shutter, and so has a high out-of- which directly push the otherpushes it. plane rigidity the ink Curl A set of actuators curl Goodfluid flow Design IJ20, IJ42 inwards inwards to reduce the to the regionbehind complexity volume of ink that the actuator they enclose.increases efficiency Curl A set of actuators curl Relatively simpleRelatively large IJ43 outwards outwards, pressurizing construction chiparea ink in a chamber surrounding the actuators, and expelling ink froma nozzle in the chamber. Iris Multiple vanes enclose High efficiencyHigh fabrication IJ22 a volume of ink. These Small chip area complexitysimultaneously rotate, Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates The actuator canLarge area 1993 Hadimioglu vibration at a high frequency. be physicallydistant required for et al, EUP 550,192 from the ink efficient operation1993 Elrod et al, at useful frequencies EUP 572,220 Acoustic couplingand crosstalk Complex drive circuitry Poor control of drop volume andposition None In various inkjet No moving parts Various otherSilverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and doesnot move. required to related patent eliminate moving applications partsTone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkrefilled. After the Operational force relatively jet actuator isenergized, simplicity small compared to IJ01-IJ07, IJ10- it typicallyreturns actuator force IJ14, IJ16, IJ20, rapidly to its normal Longrefill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillatingchamber is provided at Low actuator common ink IJ17, IJ18, IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate torefill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill Thermal ink jet channel to the nozzlechamber Operational rate Piezoelectric ink is made long and simplicityMay result in a jet relatively narrow, Reduces relatively large chipIJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01- pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22, IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most inkjet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, IJ05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofink jet, there is no problem is ink back-flow on 0771 658 A2 and doesnot expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most ink jet nozzlefiring fired periodically, complexity on the sufficient to systemsbefore the ink has a print head displace dried ink IJ01, IJ02, IJ03,chance to dry. Wben IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09,IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20,IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26,IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, afterIJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to acleaning IJ39, IJ40, IJ41, station. IJ42, IJ43, IJ44, IJ45 Extra Insystems which heat Can be highly Requires higher Silverbrook, EP powerto the ink, but do not boil effective if the drive voltage for 0771 658A2 and ink heater it under normal heater is adjacent to clearing relatedpatent situations, nozzle the nozzle May require applications clearingcan be larger drive achieved by over- transistors powering the heaterand boiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used succession rapid succession. In extradrive circuits depends with: IJ01, IJ02, of actuator someconfigurations, on the print head substantially upon IJ03, IJ04, IJ05,pulses this may cause heat Can be readily the configuration of IJ06,IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzleIJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20,IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations,it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrationsto dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Notsuitable May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle HighIJ08, IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EPclearing plate is pushed against severely clogged mechanical 0771 658 A2and plate the nozzles. The plate nozzles alignment is related patent hasa post for every required applications nozzle. A post moves Moving partsare through each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is Fabrication High Hewlett Packard formedseparately fabricated simplicity temperatures and Thermal lnk jet nickelfrom electroformed pressures are nickel, and bonded to required to bondthe print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., low costhead U.S. Pat. No. May produce thin 5,208,604 burrs at exit holesSilicon A separate nozzle High accuracy is Two part K. Bean, IEEE micro-plate is attainable construction Transactions on machined micromachinedfrom High cost Electron Devices, single crystal silicon, Requires Vol.ED-25, No. 10, and bonded to the precision alignment 1978, pp 1185-1195print head wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkinset al., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries Noexpensive Very small 1970 Zoltan capillaries are drawn from glassequipment required nozzle sizes are U.S. Pat. No. tubing. This methodSimple to make difficult to form 3,683,212 has heen used for singlenozzles Not suited for making individual mass production nozzles, but isdifficult to use for bulk manufacturing of print heads with thousands ofnozzles. Monolithic, The nozzle plate is High accuracy RequiresSilverbrook, EP surface deposited as a layer (<1 μm) sacrificial layer0771 658 A2 and micro- using standard VLSI Monolithic under the nozzlerelated patent machined deposition techniques. Low cost plate to formthe applications using VLSI Nozzles are etched in Existing nozzlechamber IJ0I, IJ02, IJ04, litho- the nozzle plate using processes can beSurface maybe IJ11, IJ12, IJ17, graphic VLSI lithography and usedfragile to the touch IJ18, IJ20, IJ22, processes etching. IJ24, IJ27,IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a High accuracyRequires long IJ03, IJ05, 1106, etched buried etch stop in the (<1 μm)etch times IJ07, IJ08, IJ09, through wafer. Nozzle Monolithic Requires aIJ10, IJ13, IJ14, substrate chambers are etched in Low cost supportwafer IJ15, IJ16, IJ19, the front of the wafer, No differential IJ21,IJ23, IJ25, and the wafer is expansion IJ26 thinned from the back side.Nozzles are then etched in the etch stop layer. No nozzle Variousmethods have No nozzles to Difficult to Ricoh 1995 plate been tried toeliminate become clogged control drop Sekiya et al the nozzles entirely,to position accurately U.S. Pat. No. prevent nozzle Crosstalk 5,412,413clogging. These problems 1993 Hadimioglu include thermal bubble et alEUP 550,192 mechanisms and 1993. Elrod et al acoustic lens EUP 572,220mechanisms Trough Each drop ejector has Reduced Drop firing IJ35 atrough through manufacturing direction is sensitive which a paddlemoves. complexity to wicking. There is no nozzle Monolithic plate.Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito etal instead of nozzle holes and become clogged control drop U.S. Pat. No.individual replacement by a slit position accurately 4,799,068 nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the Simple Nozzles limited Canon Bubblejet (‘edgesurface of the chip, construction to edge 1979 Endo et al GB shooter’)and ink drops are No silicon High resolution patent 2,007,162 ejectedfrom the chip etching required is difficult Xerox heater-in- edge. Goodheat Fast color pit 1990 Hawkins et sinking via substrate printingrequires al U.S. Pat. No. Mechanically one print head per 4,899,181strong color Tone-jet Ease of chip handing Surface Ink flow is along theNo bulk silicon Maximum ink Hewlett-Packard (‘roof surface of the chip,etching required flow is severely TIJ 1982 Vaught et shooter’) and inkdrops are Silicon can make restricted al U.S. Pat. No. ejected from thechip an effective heat 4,490,728 surface, normal to the sink IJ02, IJ11,IJ12, plane of the chip. Mechanical IJ20, IJ22 strength Through Ink flowis through the High ink flow Requires bulk Silverbrook, EP chip, chip,and ink drops are Suitable for silicon etching 0771 658 A2 and forwardejected from the front pagewidth print related patent (‘up surface ofthe chip. heads applications shooter’) High nozzle IJ04, IJ17, IJ18,packing density IJ24, IJ27-IJ45 therefore low manufacturing cost ThroughInk flow is through the High ink flow Requires wafer IJ01, IJ03, IJ05,chip, chip, and ink drops are Suitable for thinning IJ06, IJ07, IJ08,reverse ejected ftom the rear pagewidth print Requires special IJ09,IJI0, IJ13, (‘down surface of the chip. heads handling during IJl4,IJ15, IJ16, shooter’) High nozzle manufacture IJ19, IJ21, IJ23, packingdensity IJ25, IJ26 therefore low manufacturing cost Through Ink flow isthrough the Suitable for Pagewidth print Epson Stylus actuator actuator,which is not piezoelectric print heads require Tektronix hot fabricatedas part of heads several thousand melt piezoelectric the same substrateas connections to drive inkjets the drive transistors. circuits Cannotbe manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleeds on paper All IJ series ink humectant, and May jets biocide.strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoeiectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a inkjets head beforejetting Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks are mediumcan be used Printed pages U.S. Pat. No. usually wax based, No papercockle may ‘block’ 4,820,346 with a melting point occurs Ink temperatureAll IJ series ink around 80° C. After No wicking may be above the jetsjetting the ink freezes occurs curie point of almost instantly upon Nobleed occurs permanent magnets contacting the print No strikethrough Inkheaters medium or a transfer occurs consume power roller. Long warm-uptime Oil Oil based inks are High solubility High viscosity: All IJseries ink extensively used in medium for some this is a significantjets offset printing. They dyes limitation for use in have advantages inDoes not cockle ink jets, which improved paper usually require acharacteristics on Does not wick low viscosity. Some paper (especiallyno through paper short chain and wicking or cockle) multi-branched oilsOil soluble dies and have a sufficiently pigments are required. lowviscosity. Slow drying Micro- A microemulsion is a Stops ink bleedViscosity higher All IJ series ink emulsion stable, self forming Highdye than water jets emulsion of oil, water, solubility Cost is slightlyand surfactant. The Water, oil, and higher than water characteristicdrop size amphiphilic soluble based ink is less than 100 nm, dies can beused High surfactant and is determined by Can stabilize concentrationthe preferred curvature pigment required (around of the surfactant.suspensions 5%)

What is claimed is:
 1. An inkjet printhead comprising: an ink chamberincluding a nozzle; and an electrically activated buckle plate locatedin said ink chamber, wherein energy required to activate said buckleplate to eject a drop of ink from said ink chamber via said nozzle isless than one microjoule.
 2. An inkjet printhead as claimed in claim 1wherein said buckle plate is constructed from a first material having ahigh coefficient of thermal expansion and said buckle plate furthercomprises an integral heater means constructed from a secondelectrically resistive material for heating said, first material andthereby deforming said buckle plate so as to eject ink on demand fromsaid nozzle, said first material and second material being different. 3.The inkjet printhead as claimed in claim 2 wherein said second materialhas a lower coefficient of thermal expansion than said first materialand is constructed in a serpentine manner so as to allow the expansionof said heater means substantially in accordance with the expansion ofsaid first material.
 4. The inkjet printhead of claim 2 wherein saidfirst material comprises mostly polytetrafluoroethylene.
 5. The inkjetprinthead of claim 2 wherein said heater means is constructedsubstantially from copper.